The Ambler Botnet

In the past, the operators of large botnets sought to expand the size of their operations and cared little for the details of any individual compromised computer — one bot was as good, for the most part, as any other. Any one of the thousands of computers under their control could be used to send spam or participate in a denial of service attack. But now not all compromised computers are of equal value to botnet operators. As the focus of botnet activity becomes increasingly extractive — with an emphasis on stolen credit card numbers, credentials and private information — the geographic location of compromised computers has become an important factor for botnet operators. The geographic origin or stolen credit cards, or “dumps”, for example, is an important factor in pricing.

Geographic location is also important when botnet operators attempt to monetize their operations. The various compensation rates for pay-per-click and pay-per-install schemes — especially RogueAV/FAKEAV — are specific to the geographical location of the victim. Some of these schemes even restrict propagation in certain countries. There are botnets with victims that are highly concentrated by geographic location as well as targeted efforts to propagate botnets within specific regions.

This development may also be an effort by botnet operators to improve their operational security in response to the efforts by security researchers. As the risk of “take down” increases, botnet operators may be partitioning their operations to minimize the damage. As Dancho Danchev explains, this may also obscure the work of a single group by making it appear as if these disparate operations are the work of many unaffiliated groups.

The Ambler botnet is based on a trojan, Win32/Ambler, that has been actively spreading since at least October 2008. There are a variety of Win32/Ambler variants and many command and control servers. Win32/Ambler itself is a keylogger — malware that captures the keystrokes entered on a compromised computer — but also specifically targets those that use the online banking services of Bank of America. Win32/Ambler is also often found bundled with other malware.

The following post is the result of an investigation of six command and control servers – dertoplon.com, myhammers.org, sokam.info, sosanni.com and makeithappen2ce.info and zhogdiana.info – associated with Win32/Ambler. From these servers 1.8 gigabytes of data was collected. This data contains sensitive and private information from 11,251 compromised computers (38,920 unique IP addresses). It is not clear to me if the operators of these command and control servers are connected to each other, or if they are four separate botnets that happen to be using Win32/Ambler. Three of the C&C’s are hosted in China, and three are hosted in the US.

Geographic focus
These six control servers appear to be very focused with the vast majority of compromises in Italy, Russia and the United Kingdom, with one C&C focusing on the US. The majority of the compromised computers checking in with dertoplon.com’s two Ambler installations are from Italy (and the ones detected as EU may be Italian as well.) Those checking in with sokam.info and sosanni.com are almost entirely Russian. The compromised computers checking in with myhammers.org are mostly from the US. Finally, those checking in with makeithappen2ce.info and zhogdiana.info are primarily from the United Kingdom. There appears to be an effort to segment compromised computers at the country level among these command and control servers.

IP’s vs. HostsEstimating botnet size is not simply counting IP addresses. When looking at IP addresses, 38,920 unique IP addresses were found. But when counting the unique identifiers the malware assigns to each machine, the actual size of the botnet is 11,251 compromised machines. And even that number contains all machines that “checked in” with the C&C. It may include machines that are no longer compromised or no longer exist. The timestamps associated with the capture of information range from 04/16/2010 to 08/08/2010.

Captured data
The keylogger captured the keystrokes typed by the user as well as the location of the resource into which the the users entered the information. As a result broad range of content was captured including logins and passwords to email accounts, ftp accounts social networking sites and corporate and government web portals. The text of what users were searching for in search engines as well as chat conversations were also captured.

The malware connects to the command and control server and a text file is created for each individual compromised computer. Captured information, primarily keystrokes, is uploaded and stored in these text files. There are some specific tags that delineate types of data. For example, “****BOAEMAIL****” and “****BOAQUES****” are used to identify the email address and answers to security questions for Bank of America (BOA) online banking clients. It also retrieves any stored information in protected storage, such as passwords, and marks it with “*******PROTECTED STORAGE*******” in order to identify it. the files also contain a listing of file paths for specified directories “****GETFILE PATHS****” as well as a list of the volumes available “****VOLUMES LIST****”. This allows the botnet operators to target specific files and directories for extraction.

The details for each command and control server are displayed below.

dertoplon.com (edgar.marcha@verizon.net)
(dertoplon.com had two instances of the Ambler command and control backend at different directory locations).

In order to get a sense of the crimeware neighbourhood in which these control servers reside, malwaredomainlist.com is a great resource that can be used to identify other malicious domain names registered with the same email address and other domain names hosted on the same IP address.

The email addresses edgar.marcha@verizon.net and migray71@yahoo.com used to register dertoplon.com and sosanni.com were also used to register a variety of domain names that are hosting ZeuS elements as well as the Eleonore, Phoenix and Nuclear exploit kits. The IP addresses 113.11.194.148, 121.101.216.195 and 121.101.216.205 are also hosting a variety of malware including ZeuS, Russkill and YES exploit kit.

This does not mean that all of these activities are directly connected, but rather, that these activities are taking place within a malware ecosystem designed to maintain and monetize the operations of botnets. Botnets often rely on crimeware friendly hosting services, so it is not uncommon to see malicious activity concentrate around particular servers or networks. However, it does indicate that the botnet operators are connected with the malware ecosystem and leveraging the services offered within it to sustain and monetize their operations.